1. Field of the Invention
The invention relates to a tapered roller bearing.
2. Description of the Related Art
Tapered roller bearings can receive a radial load and an axial load in one direction and are used in various fields. For example, a tapered roller bearing is used to support a shaft provided in a gear mechanism for a transmission, a differential apparatus, and the like in an automobile. Such a tapered roller bearing includes an outer ring, an inner ring, a plurality of tapered rollers, and an annular cage. The outer ring has an outer-ring raceway surface that increases in diameter from a first side toward a second side in an axial direction. The inner ring has an inner-ring raceway surface facing the outer-ring raceway surface and has a cone back face rib (large rib) on the second side of the inner-ring raceway surface in the axial direction. The tapered rollers are interposed between the outer-ring raceway surface and the inner-ring raceway surface. The cage holds the tapered rollers spaced at intervals in a circumferential direction.
For example, in the differential apparatus, a bottom portion of a housing of the apparatus serves as a lubricant reservoir (oil reservoir). A rotating ring gear scoops up and splatters a lubricant stored in the lubricant reservoir to allow the lubricant to be used to lubricate the tapered roller bearing. However, in an initial stage of rotation such as starting of an engine, feeding of oil to the tapered roller bearing based on the scraping of the lubricant as described above is insufficient, possibly bringing the tapered roller bearing into a poor lubrication state. In the tapered roller bearing, large end faces of the tapered rollers come into sliding contact with the large rib of the inner ring. Consequently, when these sliding contact portions are in the poor lubrication state, temperature may be elevated due to sliding friction, leading to seizure.
Thus, a tapered roller bearing has been proposed in which a ring member (partition plate) with an L-shaped section is attached to a part of the outer ring that corresponds to an outer position of the large rib of the inner ring in a radial direction, that is, to an end of the outer ring (see FIG. 5 and FIG. 6 in Japanese Patent Application Publication No. 2008-57791 (JP 2008-57791 A)). The ring member allows the lubricant to be stored in the tapered roller bearing. Consequently, in the initial stage of rotation, the lubricant can be utilized for lubrication between the large rib of the inner ring and end surfaces of the tapered roller bearings.
The ring member with an L-shaped section described in JP 2008-57791 A is obtained by fixing an elastic member to an annular core. The configuration described in JP 2008-57791 A has, for example, the disadvantage of having difficulty in reducing component costs, and thus, the inventors have proposed a tapered roller bearing with a new configuration as described below (Japanese Patent Application No. 2014-040356). That is, as depicted in FIG. 11, the tapered roller bearing includes an annular holding member 91 provided adjacently to an outer ring 90 to enable a lubricant inside the bearing to be held. The holding member 91 has a cylindrical portion 92 and a protruding portion 93. The protruding portion 93 protrudes inward from the cylindrical portion 92 in the radial direction. The cylindrical portion 92 and the protruding portion 93 are integrally formed.
The tapered roller bearing may be assembled as follows. First, as depicted in FIG. 12, an inner ring 99, a cage 98, and tapered rollers 97 are assembled together into an inner ring unit 96. As depicted in FIG. 13, the inner ring unit 96 is moved closer, in an axial direction, to the outer ring 90 and the holding member 91 previously attached to a housing 95, to complete the assembly.
However, as depicted above, the holding member 91 is provided adjacently to the outer ring 90. The holding member 91 has the protruding portion 93 protruding inward from the cylindrical portion 92 in the radial direction. Thus, when the inner ring unit 96 is moved closer to the holding member 91 and the outer ring 90 in the axial direction, radial outermost portions 97a of the tapered rollers 97 in the inner ring unit 96 interfere with the protruding portion 93. The protruding portion 93 is elastically deformable. Consequently, the radial outermost portions 97a of the tapered rollers 97 elastically deform and climb over the protruding portion 93, enabling assembly of the tapered roller bearing. However, the holding member 91 (protruding portion 93) may be damaged. Accordingly, an operation of assembling the tapered roller bearing needs to be carefully performed and is thus difficult.